With respect to the production method of the semiconductor device, a Smart-cut method in which hydrogen is implanted into a semiconductor substrate and the substrate is attached to another substrate and then separated along a hydrogen-implanted layer by annealing, thereby completing the transferring on another substrate has been proposed (for example, refer to Nonpatent Documents 1 and 2). Further, a method in which a part of a single crystal silicon layer-including semiconductor element is transferred onto an insulating substrate by separation at a separation layer formed by implanting hydrogen into a single crystal silicon substrate in which a part of the semiconductor element such as a MOS (Metal Oxide Semiconductor) transistor is formed (for example, refer to Patent Documents 1 to 3). Use of these technologies makes it possible to form an SOI (Silicon On Insulator) substrate including a single crystal silicon layer formed on an insulating substrate. A semiconductor element such as a transistor is formed on such an SOI substrate, and thereby a parasitic capacity can be reduced and an insulation resistance can be improved. Therefore, a highly integrated semiconductor device with high performances can be provided.
For sufficient separation at the separation layer formed as a part of the single crystal silicon substrate, very highly-concentrated hydrogen of 4×1016 atoms/cm3 or more needs to be implanted into the single crystal silicon substrate, for example. Therefore, about 1×1021 atoms/cm3 of hydrogen generally exists in the single crystal silicon layer formed on the insulating substrate by the transferring. In addition, the crystal orientation is maintained even after the hydrogen implantation, but a lot of fine crystal defects are generated by crystal lattice distortion. The fine crystal defects used herein include a point defect, a transfer defect, a stacking defect, and the like, and mean those observed as a small pit through etching.
For this problem, annealing at a high temperature of 1000° C. or more is performed when the SOI substrate is formed, and thereby removal of residual hydrogen and recovery of the crystal defects can be sufficiently performed. However, if the single crystal silicon layer is formed on a glass substrate, the temperature and the time for the annealing are limited because the glass substrate has a low heat resistance. Therefore, the annealing is insufficiently performed and about 1×1020 atoms/cm3 of hydrogen and fine crystal defects exist in the semiconductor layer even after the annealing.
It is known that this residual hydrogen is chemically active and therefore, in the single crystal silicon layer, such hydrogen (1) becomes a donor, (2) deactivates impurity ions such as boron, (3) becomes an acceptor, for example, to largely change electrical characteristics of the semiconductor element. It is also known that the fine crystal defects become an electron or hole trap and traps at a density of 1×1017 atoms/cm3 or more are formed, and therefore such defects largely reduce electrical characteristics of the semiconductor element.
Therefore, in a commonly used method for producing a semiconductor device by a technology of transferring a single crystal film, within a temperature range where a glass substrate can be used, a single crystal film with an uniform orientation can be obtained on the substrate, but the residual hydrogen and the crystal defects, caused by the hydrogen implantation, make it difficult to produce a semiconductor device with sufficient device characteristics. Specifically, there is room for improvement in reduction in mobility, shift of a threshold voltage, increase in leak current at OFF state, increase in subthreshold coefficient (S value) and the like.
In addition, with respect to a polycrystalline silicon film formed on an insulating substrate by a laser crystallization method, a solid phase deposition method and the like, a method in which a hydrogen-containing layer is formed and hydrogen is diffused into a polycrystalline silicon film, thereby eliminating crystal defects in the polycrystalline silicon film has been known (for example, refer to Patent Documents 4 to 6). However, adverse effects such as change of characteristics and reduction in reliability, attributed to the hydrogen diffusion, are generated if the technology of diffusing hydrogen into a silicon film is applied to a common single crystal silicon film.
[Nonpatent Document 1]
    “Electronics Letters”, (U.S.), Institute of Electrical and Electronic Engineers, 1995, No. 14, Vol. 31, p. 1201[Nonpatent Document 2]    “Japanese Journal of Applied Physics”, the Japan Society of Applied Physics, 1997, Vol. 36, p. 1636[Patent Document 1]    Japanese Kokai Publication No. 2003-282885[Patent Document 2]    Japanese Kokai Publication No. 2004-165600[Patent Document 3]    Japanese Kokai Publication No. 2005-26472[Patent Document 4]    Japanese Kokai Publication No. Hei-05-235038[Patent Document 5]    Japanese Kokai Publication No. Hei-08-32077[Patent Document 6]    Japanese Kokai Publication No. 2001-93853